The dark picture on the outer wall is the very Madonna to which, when its position was at the Mercato Vecchio, condemned criminals used to pray on their way to execution.
Before we leave Or San Michele and the Arte della Lana, a word on the guilds of Florence is necessary, for at a period in Florentine history between, say, the middle of the thirteenth century and the beginning of the fifteenth, they were the very powerful controllers of the domestic affairs of the city; and it is possible that it would have been better for the Florentines had they continued to be so.

For Florence was essentially mercantile and the guilds were composed of business men; and it is natural that business men should know better than noblemen what a business city needed.

They were divided into major guilds, chief of which were the woollen merchants--the Arte della Lana--and the silk merchants--the Calimala--and it was their pride to put their riches at the city's service.

Thus, the Arte della Lana had charge of the building of the cathedral.

Each of the major guilds provided a Prior, and the Priors elected the Signoria, who governed the city.